Heating apparatus



Oct. 29, 1946. CLARK 2,410,013

HEATING APPARATUS Filed May 15, 1942 2 Sheets-Sheet l WITNESSES: iNVENTOR ,4- Emu. K. CLAzK r ATTOR Y Oct 29, 1946. E. K. CLARK HEATING APPARATUS Filed May 15, 1942 WITNESSES:

2 Sheets-Sheet 2 IINVENTOR EARL K'. CLARK ATTORN Patented Oct. 29, 1946 HEATING APPARATUS Earl K. Clark, Mansfield, Ohio, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 15, 1942, Serial No. 443,032

1 Claim.

This invention relates to a control for an electric heating unit, such asthe surface unit of an electric range, and it has for an object to provide an improved control.

The control commonly used comprises a switch actuated by a rotary knob and having an off position, a position of maximum heat, and several positions of reduced heat. To initiate a cooking operation, the knob is rotated from the off position to one of the heat positions, and to terminate the cooking operation the knob is rotated to the off position. The knob may also be shifted from one heat position to another during the cooking operation. This type of control is generally satisfactory but it has certain limitations or disadvantages. One of these is that the current may be turned on regardless of whether there is a cooking utensil or other article to be heated on the heating unit, thereby permitting a waste of electric current. Also, the user may remove the cooking utensil from the heating unit and forget to turn the switch to the o position, thereby resulting in a waste of electric current. A further disadvantage is that, each time a. cooking operation is initiated or terminated, it is necessary to effect rotary movement of the knob and to note the position to which the knob is actuated; whereas, the easiest control operation is one wherein a control element is moved more or less in a straight line to the end of its travel, such as pushing a button.

1 conventional construction.

It is an object of the present invention to pro- .2 vention as will be apparent from the following description and claim taken in connection with the accompanying drawings, forming a part of this application, in which:

Fig. 1 is a perspective view of an electric cooking range in which the present invention is embodied;

Fig. 2 is a fragmentary vertical section taken approximately along line IIl I of Fig. 1, showing one of the surface units and the control arrangement therefor;

Fig. 3 is a View similar to Fig. 2 except that parts are omitted for clarity of illustration, with a cooking utensil positioned On the heating unit and showing the relationship of the parts of the control arrangement when the heating unit is connected to a power source; and,

Fi 4 is a fragmentary vertical section of a range similar to that shown in Fig. 1 but incorporating a modified form of the invention.

Figs. 1, 2 and 3 Referring to the drawings in detail, I show an electric range In which comprises three surface heating units I9, 20 and 2| and a deep well cooker 22. The unit 20 is provided with a control incorporating the present invention. Any one or all of the units l9 and 20 and the cooker 22 may be provided with a similar control. Other than the novel control referred to, the range In may be of The time clock l4 controls the oven in a well-known manner.

Referring to Figs. 2 and 3, the heating unit 20 comprises a single armored resistance element 25 which is spirally coiled to provide a flat grid. The

7 ends of the resistance element 25 are provided Another object is to provide a control including a control element which may be adjusted to provide varying degrees of heat, and which need not be reset to terminate the cooking operation, nor to initiate a subsequent cooking operation if the same degree of heat is desired.

A further object is to provide a control wherein the supply of current to the surface unit is controlled by the placing of a cooking utensil or the like on the surface unit, but wherein provision is made for guarding against unintended supply of current to the surface unit when placing a cooking utensil or other article thereon for storage purposes only.

., These and other objects are effected by the inwith terminals indicated schematically at 26 and 21, for connecting the heating element to a suitable source of power. This grid is mounted on supporting arms 28 which rest on the shoulder 33 of a reflector pan 30, which in turn is supported on the range platform l2. The heating unit is adapted to support a cooking utensil placed thereon to be heated, as shown at I I2 in Fig. 3. A casing or hollow button 36 extends through the center of the heating unit and the reflector pan 30. It is vertically movable and is biased upwardly by a spring 40 to a position in which it projects above the plane of the top of the heating unit.

The heating unit 20 may be energized from a suitable source of power, such as the line conductors L1 and L2. The control for controlling the supply of current from the line conductors to the heating unit 20 comprises a line switch 45, a wattage controller 86, and a thermostatic switch 85. The line switch includes a push button It completes a connection to the line conductors L1 and L2 when a cooking utensil or the like is placed on the heating unit 20 and the button 9i is pushed in, and it opens the connection when the vessel is removed from the heating unit 20. The wattage controller 96 controls the average wattage input or rate of energization of the heating unit. In the present embodiment, in which the heating unit comprises a single heating element, the wattage controller effects such control by intermittently opening and closing the circuit to the heating unit and it is adjustable to vary the ratio of the on period to the oiT period to provide diiferent rates of energization, and to a continuous "on position and preferably also to a continuous off position. The thermostatic switch 85 supersedes the wattage controller 89 during "the initial period of a cooking operation to provide continuous current or maximum rate of energization until the utensil placed on the heating unit is brought to the boiling temperature. The wattage controller 86 and the thermostatic switch 85 are in accordance with the invention of Edward Bletz, described and claimed in his application, Serial No. lOGjlSl. The novelty of the present invention resides particularly in the line switch 45 and in its combination with the wattage controller and the thermostatic switch. These three parts of the control will now be described in greater detail.

The line switch 45 includes contacts 41 and 49 connected to the line conductors L1 and L2 and insulatedly mounted on a resilient member 53 through a dielectric member 54. It further includes a pair of cooperating contacts 49 and 50 adapted to be connected to the respective terminals 26 and 21 and insulatedly mounted on a resilient member 56 through a dielectric member 51. The upper ends of the members 53 and 56 are attached to the opposite sides of a stationary member 59.

The push button 6| is mounted on the outer end of a stem 62 which extends through the front wall of the range in alignment with the resilient member 59, so that by pushing the button 5| the resilient member 53 is moved to bring its contacts in engagement with the cooperating contacts to close the switch. The stem 62 is attached to the upper end of a member H1 which is pivoted at its lower end to a stationary block 13.

The line switch 45 is provided with a mechanism for latching it in closed position when it is closed while there is a utensil on the heating unit 20. This mechanism includes a lever TI pivoted on a stationary fulcrum by means of an oversize opening 18 in the lever and a pin 19 which extends through the opening 18. A spring 80 biases the lever in clockwise direction. The right-hand end of the lever l! extends through a slot 15 in the member 19 and is formed with an upwardly-extending hook 82 which is adapted to engage a struck-out portion 83 of the member 19 to hold the switch in closed position. The left-hand end of the lever 11 has an angular portion 84 thereon which bears against the bottom. of the hollow button 36.

When a utensil is placed on the heating unit, the button 35 is depressed and the lever Tl is tilted counter-clockwise to the position shown in Fig. 3. This operation conditions the control for closing the circuit but does not in itself close the circuit. If the button 6| is now pushed in to close the switch, the struck-out portion 83- rides over the inclined surface 8|, which is permitted by the oversize opening 18, and is latched in back of the hook 82 as shown in Fig. 3. The switch 55 is now latched in closed position and will remain closed as long as the utensil remains on the heating unit. When it is removed, the spring 89 moves the lever Tl in clockwise direction to release the member ill and permit the resilient member 53 to return to the open switch position shown in Fig. 2.

The wattage controller 86 is located in back of the backsplasher l3 and includes a thermostatic or bimetal element 92 fixed at its lower end to a stationary dielectric member 93. At its other end, the bimetal element 92 is adapted to move into and out of engagement with a stationary contact 96. The wattage controller further includes a small or auxiliary heating element 98 adapted to heat the bimetal element 92, which moves to the left out of engagement with the contact 95 as its temperature is raised by the heating element. To make the Wattage controller adjustable, the contact 96 is adapted to be moved toward or away from the bimetal element 92 by means of a knob 91 disposed on the front of the backsplasher 3. The knob may, for example, be mounted on a screw 95 threaded through the backsplasher and abutting the contact 96, the latter being movably mounted in a suitable mannor as will be readily understood by one skilled in the art.

The heating element and the bimetal element 92 are connected in series in the circuit through the heating element 25. This circuit extends from line conductor L1, through the switch contacts ll and 59, the conductor [52, the terminal 27, the heating element 25, the terminal 26, the conductor 155, the heating element 99, the bimetal element 92, the contact 96, the conductor I54, and the switch contacts 49 and 48 to the line conductor L2. As current flows through the circuit, the temperature of the bimetal element 92 is raised by the heat from the heating element 90 and as it reaches a temperature determined by the setting of the knob 91, it deflects to the left out of engagement with the contact 96, thereby opening said circuit. The flow of heat from the heating element 90 is thus terminated and as the bimetal element 92 cools to the predetermined temperature, it moves into engagement with the contact 95, thereby reestablishing the circuit. The heating element 90 again heats the element 92 and the cycle of on and ofi periods is repeated.

By turning the knob 9'! to move the contact 95 to the left, the ratio of on period to off period is increased since more heat is required to deflect the element 92 further to the left. Accordingly, the average wattage input to the heating unit and its rate of heat delivery to the utensil is increased. The contact 96 may be moved suificiently to the left to remain in engagement with bimetal element 92, thereby providing a position of continuous energization or maximum heating. By moving the contact 99 to the right, the ratio of the on period to the oil period is decreased, since less heat is required to move the bimetal element 92 out of engagement with the contact 96, and it is preferably movable sufllciently to the right to be out of engagement with the bimetal element 92 at room temp rat r h re y providing a completely off position.

The pilot thermostat 85 is locatedin the upper portion of the hollow button 36 so as to be in close proximity to the bottom of a cooking utensil placed on the heating unit 20. This thermostat includes a pair'of contacts and 88 and a-bimetal snap-acting element 89 having a pair of contacts thereon which normally bridge the contacts 81 and 88. The thermostatic switch 85 is connected, by means of a conductor I53, in shunt with the conductor I55 and the heating element 98. Accordingly, when the thermostatic switch is closed, the current is shunted therethrough and the heating element 88 is deenergized, thereby maintaining the bimetal element continuously in engagement with the contact 96.

Figs. 1, 2 and 3.Operation To initiate a cooking operation, the user first places the utensil M2 on the heating unit 28, which action tilts the lever I1 into counterclockwise direction, in which position it is adapted to latch the member I8. The user then pushes the button 6| to close the line switch 45, which is thereby latched in closed position by .the engagement of the member 18 with the lever 11. Assuming that the wattage controller 86 has been left at a setting which is still suitable, this pushing of the button is the only control operation necessary to be effected by the user for the entire cooking operation.

Since the temperature of the utensil I I2 is normally below the boiling temperature at the beginning of a cooking operation, the thermostatic switch 85 remains closed. Accordingly, the heating element 98 of the wattage controller is shunted and does not heat. Accordingly, the flow of current through the heating unit is continuous and delivers heat at its maximum rate to the utensil II2.to raise its temperature as quickly as possible to the boiling point. When the boiling point is reached, the thermostatic switch opens its contacts, causing the current to flow through the heating element 98. The wattage controller 86 thereby assumes control of the heating unit in accordance with the setting to which it has previously been adjusted. Such setting will normally provide a relatively low rate of energization such as that known. as simmering. Such heating continues until the user lifts the utensil from the heating unit, at which time the lever 11 is tilted in clockwise direction to unlatch the member I8. Due to the resilience of the member 53, the line switch 45 thereupon opens the connection to the line conductors L1 and L2 to terminate all supply of heat.

It will thus be apparent that it is not necessary to turn the knob 91 to the off position at the end of a cooking operation, nor is it necessary to adjust it to the desired heating position every time that a cooking operation is initiated. The same setting of the wattage controller 86 will be found satisfactory for most cooking operations, so that the knob 91 may be left in the same position from one cooking operation to another and adjusted only when an unusual cooking operation is encountered. This means that, for most cooking operations, the only control operation necessary for the user to carry out is to push the button 6|.

Figure 4 Referring now to Fig. 4, I show an embodiment in which electrical mechanism instead of a mechanical latch is employed for retaining a line switch in closed position only so long as there is a utensil positioned on the heating unit. In this embodiment, the heating unit 28a comprises two armored resistance elements I33 and I34 which are spirally coiled to provide a grid mounted on supporting arms I36. The ends of the latter rest on theshoulder I84 of a reflector pan I83, the latter being again supported on the platform of the range. A pin I extends vertically through the center of the heating unit and is biased upwardly by a compression spring II8, the upper end of which engages a pressure plate I89 which in turn bears against a shoulder on the pin I85. The ends of the two resistance elements are provided with terminals represented schematically by the reference characters 88 to I8I for connecting the heatin unit to a suitable source of power.

The heating unit 28 may be energized from a suitable source of power, such as an Edison threewire system including two outside conductors L1 and L2 and a neutral conductor N. A switch I I4 is provided for connecting the resistance elements I33 and I34 to the line conductors in a manner well known in the art to give a plurality of difierent heats; for example, to connect the heating elements in parallel across the conductors L1 and L2 to give a high heat, to connect one of them across the same conductors to give a medium high heat, to connect both of them in series across the same conductors to give a medium heat, to connect one of them across the conductors L1 and N to give a low heat and to connect both of them in series across the conductors L1 and N to give a simmer heat. The switch II4 may be of a construction already well known in the art, so that further description thereof is not necessary. This switch is mounted on the back of the backsplasher I3, but may be disposed elsewhere. It includes a knob H5 provided on the front of the backsplasher for setting the switch to obtain the different degrees of heat specified above.

The switch H4 is connected to the conductors L1, L2, and N through conductors IIB, I28 and H9, respectively. Conductors I23, I24 and I26 connect the switch I I 4 to the terminal 98, the two terminals 99 and I 88 in common, and the terminal I8 I respectively.

A two-pole switch I38 and a two-pole switch I3I are interposed in the conductors H8 and I28, so that if either of these switches is open, the heating unit cannot be energized. The switch I38 is actuated by the pin I85, described above, and is closed when the pin is depressed. The switch I3I includes a rod I 45 on which the contact-bridging elements are mounted. Its forward end extends through the backsplasher and a push button I46 is mounted or formed thereon. It is biased to open circuit position by a spring I48 acting through a pressure plate I41. A solenoid including a core I58 mounted on the rod I45 and a coil I5I is adapted when energized to hold the switch I3I in closed position. The coil I5I is energized by a circuit I53 controlled by its own contacts.

Figure 4.Operation The operation of the embodiment shown in Fig. 4 is as follows: The cooking utensil or the like to be heated is positioned on the heating unit 28a, thereby closing the switch I38. The circuit is still open, however, at the switch I3 I. The user then pushes the button I48 to close the switch I3I. The circuit is now completed to the switch II4, thereby placing the latter in control of the energization of the heating unit 28a. If the switch knob I I5 is already in a heat position, then energization of the heating unit 28a is effected upon closing of the switch I3I at the rate determined by the position of the knob II5. If it is in the ofi position, then the heating unit is not ener- 7 gized until such time as the knob is moved to a heat position. It may be noted that the knob I I5 may be turned at any time, but that the switch II4 can be effective to energize the heating unit only at such time as both switches I30 and I3I are closed.

Upon completing the cooking operation, the user merely lifts the utensil from the heating unit. This opens the switch I30 to interrupt the supply of electric current to the heating unit. Since the holding circuit for the solenoid I53 is also deenergized by such current interruption, the switch I3I is opened by the spring I48. Accordingly, the circuit cannot be reestablished until such time as both of the switches I30 and I3I are again closed by placing a utensil on the heating unit and pushing the button I46, respectively. In terminatingthe cooking operation, it is not necessary to turn the knob I I5 to the off position, but it may be left undisturbed until such time as it is desired to energize the heating unit at a different rate than that for which the knob is set. In other words, where the same degree of heat is desired, the knob may be left in one position from one cooking operation to another and only actuated when a diiferent degree of heat is desired.

Instead of having the pin I05 controlling the switch interposed in the conductors H6 and I20, it may actuate a switch in the holding circuit for the coil I5 I. In such case, the heating unit could be energized without placing a utensil thereon by merely pushing the button I46, but it would be energized only so long as the button is manually held in the closed circuit position. As soon the button I46 is released, the spring I48 would reopen the switch I3I to deenergize the heating unit. Upon placing a utensil on the heating unit, however, pushing the button I46 would complete the holding circuit and the switch I3I would be held in closed position until the utensil is removed from the heating unit.

The single claim is directed to the embodiment shown in Fig. 4.

What is claimed is:

The combination with an electrical heating unit adapted to supply heat to a cooking utensil or the like and a source of power for said heating unit, of a switch for connecting said heating unit to said power source, said switch being biased to open position, means for moving said switch to closed position, electro-magnetic means for holding said switch in closed position, a circuit connecting said electro-magnetic means to said power source for energizing the same, said circuit being so arranged that it is open at all times that said switch is open, a second switch connected in said circuit, said second switch being moved to closed position by placing a cooking utensil or the like on said heating element, thereby completing the circuit from said power source to said electro-magnetic means and making the same effective to hold said first switch in closed position when moved to such position, said second switch being biased so as to move to open-circuit position when there is no cooking utensil or the like on said heating unit thereby opening the circuit from said power source to said electromagnetic means and rendering said electro-magnetic means ineffective to hold said first switch in closed position when there is no cooking utensil or the like on said heating unit.

EARL K. CLARK. 

